flex tree动态更换各个节点的图标

 [Embed(source="Image/Point.jpg")]
   public var mPoint:Class;
   [Embed(source="Image/Line.jpg")]
   public var Line:Class;
   [Embed(source="Image/Region.jpg")]
   public var Region:Class;
   [Embed(source="Image/Text.jpg")]
   public var Texts:Class;

 private var mDsName:String="SDE";

   [Bindable] 
   private var company:XML = 
    <list>
      <department title={mDsName} code="200">
      </department>                              
    </list>;
   
   [Bindable] 
   private var companyData:XMLListCollection = new XMLListCollection(company.department); 

   /*
   加载Tree
   */
   private function AddDtSet(mDataSource:se_mobile_datasource ):Boolean
   {
    if (mDataSource==null)
    {
     return false;
    }
    if( mDataSource.m_vDatasets==null)
    {
     return false;
    }
    var mDtV:Vector.<se_mobile_dataset>=mDataSource.m_vDatasets;
    for(var i:int=0;i<mDtV.length;i++)
    {
     var mDtName:String=mDtV[i].m_sDtName;//数据集集合
     var mType:int=mDtV[i].m_nDttype;//类型
     addEmployee(mDtName,mType);
    }
    return true;
   }
   
   private function treeLabel(item:Object):String
   { 
    var node:XML = XML(item);
    if( node.localName() == "department" ) 
     return node.@title;
    else
     return node.@name;
   }
   private function addEmployee(tt:String,type:int):void 
   {  

    var newNode:XML = <employee/>;
    newNode.@name =tt;
    var dept:XMLList =company.department.(@title == "SDE");
    if( dept.length() > 0 ) {      
     dept[0].appendChild(newNode);      
     tree.setItemIcon(tree.dataProvider.getItemAt(0), rootOpenIcon, rootOpenIcon);
     //更换子节点图标
     switch(type)
     {
      case 1://点
       tree.setItemIcon(tree.dataDescriptor.getData(newNode),mPoint,mPoint);
       break;
      case 2://线
       tree.setItemIcon(tree.dataDescriptor.getData(newNode),Line,Line);
       break;
      case 3://面
       tree.setItemIcon(tree.dataDescriptor.getData(newNode),Region,Region);
       break;
      case 4://文本
       tree.setItemIcon(tree.dataDescriptor.getData(newNode),Texts,Texts);
       break;
      
     }

}
    }   
     /*

获取选中节点名称  
      */
   protected function tree_changeHandler(event:ListEvent):void
   {

     Alert.show(tree.selectedItem.@name);

}

 

 <mx:Tree id="tree"  left="{SetScreenSize(2)+230}"  x="0" y="20"  width="188" height="339" backgroundColor="white"
    borderColor="black" change="tree_changeHandler(event)" dataProvider="{companyData}"
    iconField="@icon" labelFunction="treeLabel"> 
 </mx:Tree>